(1) Field of the Invention
The invention relates to ferrous metallurgy, in particular, to slab production by continuous casting in ferrous metallurgy.
During continuous steel casting an important technical task is destruction of consistency in dendrite formation at the first stage of steel crystallization in a mold.
(2) Description of Related Art
Use of a submerged nozzle for steel transfer from an intermediate ladle into the mold is known from description of a continuous casting method (refer to, for example, patent RF No 2165825, B 22 D 41/50, published 27 Apr. 2001, Mb 12).
The main disadvantage of the known submerged nozzle lies in the fact that the technique implemented in this case in a greater or lesser degree relates to steel casting into blanks with a low ratio B:h, where h—height of blank section; B—width of blank section. Thus, the use of the known submerged nozzle is not efficient at continuous steel casting resulting in slab production if B>>h.
Description of a submerged nozzle for steel continuous casting (refer to, for example, patent RF Mb 2148469, B 22 D 11/10, published 10 May 2000, j\b 13), in which metal flow direction is changed as it leaves a closed-bottom submerged nozzle and enters a mold and metal is directed to corners of a square mold through side outlet channels, is known. The following disadvantages are inherent to the known submerged nozzle: metal jet leaving the side channels of the nozzle hits the mold walls directly that is not desirable as the possibility of destruction of a forming sinterskin of the crystallized metal increases, a risk of accidental metal entry occurs; metal does not curl in the mold what excludes an active influence on dendrites formed during crystallization, reduces the quality of the blank; thus the submerged nozzle is intended to be used for square blank casting only.
A submerged nozzle comprising a bottom and outlet side channels, located fan-shaped in a circumferential direction with displacement and curvature of their longitudinal axes relatively to the nozzle longitudinal axes, in the lower part is known (refer to, for example, patent RF Ns 2167031, B 22 D 41/50, published 20 May 2001, Ns 14).
The disadvantages eliminating full-scale implementation of the tasks, which arise at continuous slab casting, are inherent to the known submerged nozzle. These disadvantages are as follows: nozzle design does not exclude a direct force contact of steel jets leaving the nozzle with the mold walls, what is extremely undesirable taking into account the conditions of metal crystallization; design of the outlet side channels in the nozzle excludes an intensive coverage of steel volume, located below the level of these channels, by rotation. Thus, coverage of the most part of the hot metal in the mold by rotation is difficult.
A submerged nozzle for continuous steel casting from an intermediate ladle into a mold comprising a bottom, side channels and a skirt fixed to the lower part of the nozzle above the outlet side channels, in the lower part is known (refer to, for example, patent RF JVe 2236326 with priority dated 4 Nov. 2002).
Based on a set of the essential features the specified submerged nozzle is the most similar to the proposed one, thus it is taken as a prior art.
The known submerged nozzle has an essential disadvantage being in the fact that it can not be used effectively at continuous slab casting if B>>h as in this case coverage of the bulk steel, contained in the mold, by rotation is eliminated. The proposal of curling the steel supplied into the mold using two submerged nozzles with the skirts, curling the steel like engaged gears, examined in the patent under consideration is efficient at minor deviations of B/h (maximum 2.5 . . . 3) which are not characteristic to the main sizes of continuously-casted slabs if B/h has the value of 4.4 . . . 7.4 and greater.